A transmission system of this kind is assumed to have several configurations: a configuration in which it allows transmission of a motion, i.e. it is in the engaged state; and a configuration in which said transmission does not occur, i.e. it is in the disengaged state. The electrical actuator thus makes it possible, via an electric motor, to hold the transmission system in at least one of said configurations, and to transition from one to the other of said configurations.
Holding the transmission system in a configuration using the actuator requires the latter to exert a holding torque on the transmission system, and the exertion of said torque is associated with supplying electricity to the actuator motor by way of a holding current. In order to reduce the size of the electrical energy source dedicated to supplying electricity to the motor, it is important for said holding current to be low. In addition, since said holding current can cause heating in the motor due to the Joule effect, reducing said current allows a reduction in the risk of premature wear on the actuator or even destruction thereof by fire. Said holding current I can be associated, by way of a constant K, with the electromagnetic torque T exerted on the electric motor via the equation T=K*I; this requires that the motor be dimensioned so that the constant K has a high value.
The transmission system's transition from one to the other of the above configurations must be performed quickly in the interest of a satisfactory response to a setpoint. Such quickness requires that the motor be capable of achieving high speeds, which requires a constant K having a low value.
Implementation of an electrical actuator allowing a reduction in the holding current while responding satisfactorily to dynamic setpoints thus involves meeting contradictory requirements.
To this end, it is known to combine an electric motor of small size with a reduction gearbox having a mechanically variable ratio, in order to adapt the speed and the current of the electric motor in response to setpoints, and having a wear takeup system for the transmission system. It is furthermore known to combine an electric motor of small size with a fixed-ratio reduction gearbox having an elastic system providing specifically the required power output to the motor, and having a wear takeup system for the transmission system.
Such solutions are complicated to implement and require the addition of specific parts including a wear takeup system for the transmission system, and are consequently costly and bulky.